When do Russian Blues go on heat?

My little mini munch Scarlett is 6 months old and is showing no signs of going on heat. My vet is of the "let her have one cycle and then we will spay her" school of thought. So just wondering, does anyone know when do Russian Blues usually go on heat?

From what I've seen, most cats will go into heat the first spring after they're born, whether this is at 4 months or 8 months or whenever---depending on when they were born. It's usually sometime between January-March, sometimes as late as April. So probably soon, although some purebreds tend to be late bloomers, but that's usually longhairs.

Thanks! My challenge is I live in Singapore where it is hot and humid every day (seriously 32 degrees centigrade every 365 days a year). So we don't have seasons other than monsoon ones. So she isn't going to get a spring bless her. Does that make a difference?